I too am the mom of a compulsive gambler. It is so hard to give advice to somebody at the beginning of this “journey”. You are right when you say you are afraid it is just the tip of the iceberg. My experience has shown this is not a simple, clear cut issue whereby you do x,y & z and you are good to go.
My best suggestion would be to garner all the support you can for yourself… this forum, the chat, GamAnon and reading up on gambling addiction. Forewarned is forearmed and nothing can ever replace face to face support. He is your son and unfortunately some of your first instincts can end up being the most counter productive to his recovery. Support can help give you a proper perspective.
I have been dealing with this for a long time and I am still alive and kicking. I have found ways to compartmentalise my sadness, anger and fear and truly enjoy my life and family the majority of the time. It does take work and a commitment to yourself.
Here is my favourite quote that has helped me through this
“When we are no longer able to change a situation – we are challenged to change ourselves”
Please take care and keep writing!
Cathyx